“[T]he areal extent of heavy rainfall is truly overwhelming, literally and figuratively,” the report said about the storm, whose catastrophic flooding engulfed Southeast Texas in August’s final week last year, killing 68 people.

Such extreme rain amounts — which only have a 1 in 1,000 chance of happening in a given year — covered an enormous area, an accompanying geographic analysis showed.

Different color shades show the likelihood of the amount of rain in different areas of Southeast Texas in a given year. For example, the dark blue shaded area indicates less than a 1 in 1,000 chance of happening in a given year in that location. (NOAA Office of Water Prediction)

The report confirmed that peak rainfall totals reached record-crushing levels, just over 5 feet near Nederland and Groves, Tex., near Port Arthur. “Both of these values (and from five other stations) exceed the previously accepted United States tropical cyclone storm total rainfall record of 52.00 inches at Kanalohuluhulu Ranger Station, Hawaii, in August of 1950 from Hurricane Hiki,” the report said.

Isolated rainfall amounts might have even been more extreme. The report noted that radar estimated totals “as high as 65-70 inches in southeastern Texas.”

The excessive rainfall was caused in large part when the monster storm stalled over the Lonestar state, drawing moisture from the warm Gulf of Mexico and dumping punishing torrents over an extended duration. Additional factors helped intensify and focus some of the extreme rainfall. “While Harvey was very slow moving over Texas, not all drifting cyclones produce such torrential rain totals,” the report explained. It said Harvey interacted with a weak cold front over the region, which “hardly moved” and intensified the rainfall.

The consequence of such excessive rainfall was one of the most expensive natural disasters in U.S. history. “Harvey is the second-most costly hurricane in U.S. history, after accounting for inflation, behind only Katrina (2005),” the report said.

The report does not discuss the possibility that Harvey’s rains were affected by human-induced climate change, but independent analyses published in peer-reviewed journals found the heating of the air and sea from climate warming may have boosted Harvey’s rainfall output by at least 15 percent.

In addition to extreme rainfall, the Hurricane Center report said Harvey raked the area just northeast of Corpus Christi with Category 4-intensity sustained winds (around 130 mph) at landfall and generated a coastal surge of 8 to 10 feet above ground level.

Jason SamenowJason Samenow is The Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association. Follow